The invention disclosed and claimed herein pertains generally to the field of neutron detection devices and, more particularly, to neutron detection devices of the type which employ lithium-6, in a solid form, to respond to neutrons by radiating charged particles into an ionizable counting gas.
At present, most high-sensitivity neutron detectors of the radiator, ionizable gas type employ either .sup.10 BF.sub.3 or .sup.3 He, in a gaseous state, as the radiating medium for the detector, i.e., for the detector component which interacts with neutrons and subsequently radiates ionizing particles in response thereto. .sup.3 He is always in a gaseous state at practical temperatures and pressures. .sup.10 BF.sub.3 must be employed in a gaseous state, since the principal ionizing particle which results from the reaction between a neutron and a boron nucleus of .sup.10 BF.sub.3 in an alpha particle which is of extremely short range, e.g., 5.times.10.sup.-3 mm. If a reaction generating an alpha particle were to take place within a solid material, the dimensions of the material would have to be extremely small, to prevent the alpha particles from being trapped therewithin.
Because of the low density of .sup.10 BF.sub.3 and .sup.3 He at ordinary pressures, they must be contained in chambers of large volume in order to be used as the radiator component in a neutron detector. Consequently, such detectors tend to be comparatively large or bulky. While neutron detectors are available which have used a solid layer of .sup.10 B as an alpha particle radiator, the layer must be kept very thin, as aforementioned, e.g., 10.sup.-2 mm, and it may still be necessary to supplement the .sup.10 B radiator with one of the above gaseous radiator components. In the past, solid lithium-6 (.sup.6 Li) has been used as the neutron sensitive component in a radiator, ionizable gas neutron detector wherein the lithium-6 is coated upon the curved inner surface of a cylinder. See, for example, U.S. Pat. No. 2,721,944, issued Sept. 9, 1950, which discloses a neutron detector for use in geological exploration of oil fields. Also, in a prior patent application of Charles A. Young, (U.S. patent application Ser. No. 06/203,006, filed Nov. 3, 1980, now U.S. Pat. No. 4,365,159), incorporated herein by reference, a neutron detector was disclosed in which a number of flat sheets of lithium-6 are employed in a neutron detector such that the sheets are stacked in parallel layers within a thin, flat container. In that scheme, a separate layer of counting wires was required for each lithium-6 foil layer.